In general, a socket apparatus for testing a semiconductor device (IC) is provided in a test board or a burn-in board. Here, a burn-in chamber that outputs driving power and electric signals, or peripheral devices and an additional apparatus for an IC test, etc. are electrically connected to each other through input and output (I/O) leads of the boards. Thus, the socket apparatus is employed as a system for the IC test.
Among well known and widely used ICs in the electronic industry, a ball grid array (BGA) is a type of the IC that is notable for innovatively reducing a size and thickness thereof by arranging leads of the IC, namely, balls of the IC, on the whole bottom surface of the IC.
In the mean time, a land grid array (LGA) is a type of the IC without having the balls on a pad (or a land) as in the BGA type IC.
Recently, such ICs have been manufactured in a variety of forms including an LGA type IC or a BGA/LGA hybrid IC. Specifically, a socket for testing the LGA type IC or the hybrid type IC is provided with a plurality of contacts having predetermined elasticity in a vertical direction, and the lower leads of the contacts are connected to a printed circuit board (PCB) by contacting or soldering.
Here, the upper leads of the contacts are formed such that they come into contact with the leads of the IC loaded in a socket. Further, the socket should be provided with a pressure device for pressing the IC downwards for achieving stability of electric contact therebetween.
For reference, when physical force applied to the upper surface of the IC by the pressing device is divided by the number of contacts, physical force applied per one contact is calculated.
More specifically, physical force applied to one contact is approximately 10 gf. For example, when the number of leads of the IC is five hundred, it is estimated that physical force of about 5.0 kgf is required to be applied to the IC.
Accordingly, the socket apparatus for testing the IC should be provided with a latch capable of effectively applying strong physical force to the IC as described above.
As there has been a trend towards increasing a lead count, and reducing a lead pitch and thickness of the IC in recent years, it is required that the socket be provided with a pressure means capable of effectively pressurizing and fixing the IC to the socket while maintaining a level position of the entire surface of the IC in response to contact force applied to leads of the IC during a burn-in test at high temperature for a long time.
FIGS. 1a, 1b, and 1c are a plan view, a side view, and a bottom view respectively showing a typical IC. Specifically, the BGA type IC having a lead pitch of 0.35 mm, a lead count of 456, a size of 14×15.5, and thickness of 0.5 mm is shown as a representative IC produced in recent years.
With reference to FIGS. 1a to 1c, an upper surface of a semiconductor device 1 is provided with fine protrusions 2, thereby having a sandpaper-like surface. Further, a lower surface of the semiconductor device 1 is provided with a plurality of balls 3 as leads of the semiconductor device 1.
In the future, it is predicted that thickness of the semiconductor device may be reduced to 0.25 mm, a lead pitch may be reduced to 0.30 mm, 0.25 mm, 0.2 mm, etc., and the lead count may be increased to 500 to about 1000.
FIGS. 2a and 2b are a top plan view and a cross-sectional view taken along line A-A of FIG. 2a respectively showing a socket apparatus for testing a semiconductor device in the related art.
With reference to FIGS. 2a and 2b, the conventional socket apparatus 10 for testing the semiconductor device includes a socket body 11 provided with a plurality of contacts 12 having a curved shape, a cover 13 moving up and down on the socket body 11, and a latch 14 rotatably assembled to the socket body 11 so as to fix or release the semiconductor device 20 in conjunction with up-and-down movement of the cover 13.
The latch 14 is provided with a guide slot 14a to which guide pin 15a is engaged, and the guide pin 15a is fixed to a driving link 15 of which a first end is hinge-coupled to the cover 13. Further, the cover 13 is resiliently supported by a coil spring 16.
In such conventional socket apparatus, when pressing the cover 13, the latch 14 opens outwards, thereby loading the semiconductor device 20 therein. On the other hand, when releasing the cover 13, the latch 14 presses down and fixes an upper surface of the semiconductor device 20 due to resilience of the coil spring 16.
However, a front end of the latch repeatedly presses down and fixes the upper surface of the semiconductor device by applying strong force thereto. Moreover, the upper surface of the semiconductor device is an uneven surface. These result in intensifying abrasion caused at the front end of the latch that comes into contact with the semiconductor device as frequency of a test is increased. Thus, there is a problem in that it is difficult to achieve stability of electric contact between the leads of the semiconductor device and the contacts, and reliability of the test is reduced.
Usually, when tested about fifty thousand times, the socket apparatus reaches a point where it cannot be operated anymore due to abrasion caused at the front end of the latch 17.
Moreover, the conventional socket apparatus for testing the LGA type IC requires additional components to arrange and assemble contacts having a bow-shaped curved portion. Thus, there is a problem in that it is difficult to assemble the contacts due to a plurality of the components thereof. In addition, the conventional socket apparatus requires a structure for pressing and fixing the semiconductor device with strong physical force, and a driving device, thereby further complicating the structure thereof. Particularly, there is a problem in that such a complicated structure leads to an increase in a production cost and reduction in overall quality of the socket apparatus.
Furthermore, as shown in FIG. 2, when using a bow beam contact or a buckle beam contact, there is difficulty in securing insulation between contacts and assembling the socket apparatus. Thus, the socket apparatus is problematic in that the cost thereof is increased and quality thereof is reduced. Moreover, another problem resides in that cracks, deformation, distortion, etc. are caused in a wafer of the IC or the IC after performing a burn-in test for a long time.